There was squeaking coming from the rear end on even the smallest bump, so I greased both fittings and sprayed GM PTFE SuperLube on all the pivot points/ bushings, then worked it all in by pushing the rear end up and down several times as far as I could.

The squeaks are gone and the rear end is very smooth. Prior to that the rear end was very stiff, now it's only moderately stiff.

Hope this helps!